Radio/Transcript
Transcript Text reads: The Mysteries of Life with Tim and Moby A boy, Tim, reads from a typed letter. TIM: Dear Tim and Moby, How does a radio work? From, Chucky. A robot, Moby, joins Tim. MOBY: Beep. TIM: Well... An opening appears in Moby's forehead, and an antenna pokes out. A radio transmission of a baseball game can be heard. RADIO SPORTSCASTER: Steps up to the plate. Oh! Missed it by a mile! He's zero for twelve, in this, the fourth game of… TIM: Turn that off. MOBY: Beep. TIM: Yeah, I want to listen to the game, too, but we're working. Most people don't have antennas popping out of their heads, but antennas are part of a radio receiver. When you turn on your car radio, the antenna goes up to receive radio waves. An animation shows a car's radio antenna extending upward. TIM: If you're using a radio in your house, the signal comes in a whole lot better if you move the antenna around a little. An animation shows a person indoors holding up a portable radio to catch a signal. TIM: This signal that I'm talking about is made of radio waves. We talk about all sorts of electromagnetic waves in the Waves movie, so check that out if you want to get some waves facts. Radio waves are invisible waves that each travel at a different frequency. An animation shows radio waves. TIM: These waves are super-fast. They move at the speed of light. Radio waves are used by people to broadcast sounds and pictures to every corner of the world. An animation shows several radio wave transmission towers placed all around the world. TIM: Radio transmissions can give us news of events around the world just moments after they happen. Radio waves are sent from a device called a transmitter. An animation shows a microphone, a receiver, and a radio transmitting antenna. Tim appears and speaks into the microphone. TIM: Hello. Tim pulls back from the microphone. TIM: A microphone translates sounds into electrical signals. These signals are used to change, or modulate, a carrier wave. The carrier wave determines where you'll find the signal on your radio dial. The combined signals are amplified and sent into the air through an antenna as radio waves. An animation demonstrates the process Tim describes. TIM: Once the transmitter has released to a signal, you can pick it up using a receiver. A receiver antenna picks up the radio waves and converts them back into electrical signals. The receiver separates the signals from the carrier wave, amplifies the signals, and then plays them through a speaker, which converts them back into sound. An animation shows radio waves moving from a transmitter to a receiver. The receiver picks up and converts the waves, then plays them through a speaker. TIM'S VOICE OVER THE SPEAKER: Hello. TIM: You've probably heard of AM and FM radio, but have you ever wondered what those initials stand for? AM is amplitude-modulated, meaning that the signal is measured by its amplitude, or height. An animation shows the changing amplitude of an AM signal. TIM: AM waves are long and shallow, making them low-frequency waves. FM is frequency-modulated, meaning that the signal is measured by its frequency, or the number of waves per second. An animation shows the changing frequency of an FM signal. TIM: FM waves are high-frequency waves that have a short wavelength. So how do these waves travel from one part of the world to another without flying off into space? There's a part of the earth's atmosphere called the ionosphere that stretches from fifty to eighty kilometers above the earth's surface. An animation shows the earth's surface and its atmosphere. One layer of the atmosphere is labeled: ionosphere. It is located where Tim describes. TIM: Low frequency radio waves can travel to distant lands by bouncing off the ionosphere. A transmitting antenna sends radio waves upward. The waves hit the ionosphere and bounce back down to the earth's surface, where a radio picks them up. TIM: Short waves can travel longer distances by bouncing off a higher point in the ionosphere. Other radio waves are transmitted and bounce off a higher point in the ionosphere than the earlier ones, then bounce to a radio farther away. TIM: That's why with a short-wave radio in New York, you could hear the weather report in Paris. Not that that would do you any good. Some very low frequency waves travel straight through the atmosphere without needing to be bounced. Other radio waves move straight from the transmitting antenna to a radio. TIM: Very high frequency signals pass right through the ionosphere, so we use satellites to bounce these signals back to Earth. A satellite moves above the ionosphere. Signals go through the ionosphere and bounce off of the satellite. MOBY: Beep. TIM: Yeah, but a wave doesn't bounce straight up and down. It's more like a billiard ball when it gets banked off to the side of a table to make a shot. Tim crouches at the side of a pool table. He is holding a pool cue, preparing to take a shot. MOBY: Beep. TIM: Well, watch this. Tim shoots a cue ball across an empty pool table. It bounces off one side of the table and just misses going in a corner pocket. TIM: Uh, if you could just pretend that went in, that would be great. Thanks. So, when you tune your radio to, say, ninety-five point seven FM, that means your radio is listening for radio carrier waves with a frequency of ninety-five point seven megahertz, or ninety-five point seven million waves per second. An animation shows a radio being tuned to the frequency Tim describes. Text reads: MegaHertz equals millions of waves per second. TIM: Since their discovery, radio waves have changed human existence by enabling rapid communication and bringing the world just a little closer together. So, uh, Moby. MOBY: Beep? TIM: Turn the game on. MOBY: Beep. Category:BrainPOP Transcripts